The Ketogenic diet is based on ketogenesis, which is the process in which ketones are produced by the liver during the break down of fatty acids. When the body does not have adequate carbohydrates for energy it must turn to fats for energy, this prompts the liver to break fatty acids into ketones which are used for energy in place of the glucose.

The Ketogenic diet was used in the early 20th century as a treatment for epilepsy. The ketotic state causes an anticonvulsant effect reducing the severity and occurrence of seizures. With the advent of anti-seizure medications the ketogenic diet fell out of favor.
So, is the keto diet just another name for a low-carb diet? Yes and no. The low carbohydrate diet popular today uses a moderate level of protein and fat to lower carbohydrate intake. The keto diet increases fat intake to replace carbohydrates and does not alter protein levels, keeping them at just what is needed for maintenance. The traditional keto diet uses a 4 to 1 ratio of fat to other nutrients. It uses just enough protein to maintain growth and repair and keeps overall caloric intake at a level sufficient to maintain the proper weight for height and age.

The theory behind the use of the keto diet for fat loss is that once the body is in a state of ketosis it will continue to burn fat for energy and when the fatty acids in the blood are used up the body will turn to fat stores. Carbohydrates are kept to a minimum to reduce their availability for energy. The body uses the available carbohydrates first for energy, which is usually used up in the digestion process, and then shifts to ketosis for the rest of the energy needs.

Many people who use this diet use some form of testing to make sure they are in a ketogenic state. There are test strips that use urinalysis to determine the amount of ketone bodies present. This serves a two part purpose. First, it tells the dieter whether they are in a state of ketosis. Second, it helps the dieter monitor overall ketone levels to avoid the metabolic condition, ketoacidosis. This is when the ketone bodies build up in the blood stream and decrease blood pH substantially, leading to many other medical issues. Although a severe condition, and it must be taken seriously, it is rare on a regular keto diet.

A keto diet can be enhanced by endurance training using long slow exercises like walking, jogging, biking, swimming, etc. The body kicks into ketosis when long term energy is needed. The body uses up the available glucose, and glycogen stores, fairly quickly and then must turn to fat for energy. If the body is already using its fat burning furnace it does not have to switch over for the long term needs of endurance training.

Some people use medium chain triglycerides (MCTs) on the keto diet due to their more ketogenic properties. Most food has long chain triglycerides (LCTs) but 30 to 60% of the total calories may be replaced with MCTs on an MCT Keto diet. MCTs can be bought in supplement form to add to the diet.